| Episode Narrative |
While the majority of severe weather within the region on this late Saturday afternoon and evening focused to the east of South Central Nebraska, the very first supercell storm of the day resulted in several reports of hail from 1 to 2 inches in diameter across northeast portions of the area. This storm initiated in southern Howard County around 5 PM CDT and quickly became severe. As it tracked across southern Merrick and central Hamilton Counties, it briefly exhibited some enhanced rotation. Though no tornadoes occurred, a funnel cloud was reported in the Chapman area around 6 PM CDT. Just southeast of Marquette, hail up to 2 inches in diameter fell for 10 minutes. The storm exited eastern York County around 730 PM CDT, just as it was transitioning into more of a damaging wind-producer. Although this lone supercell resulted in the only reports of severe weather across the area, other strong storms raked across portions of Nance, far northeastern Merrick and far northern Polk Counties a bit later in the evening, mainly between 830 and 930 PM CDT.
The initial supercell development late in the afternoon occurred in a very unstable mesoscale environment characterized by around 4000 J/kg mixed-layer CAPE, stemming from surface temperatures around 90 degrees and dewpoints in the 70s. Deep-layer vertical wind shear was also quite favorable for mid-summer, averaging 30-40 knots thanks to a seasonably strong quasi-zonal flow aloft. The primary triggering mechanism aloft for severe storm development was a modest mid-level shortwave tracking along the Nebraska-South Dakota border, while at the surface, a weak cold front gradually sagged southeastward across the area. |
